1. Field of the Invention
The present invention relates generally to pumps and more particularly, but not by way of limitation, to an improved submersible pump.
2. Description of the Prior Art
There is a market in this country and abroad for submersible pumps that are efficient, lightweight, and inexpensive to manufacture. A pump manufactured for submersion in process fluids must be protected from the environment in which it operates, such as when it is submersed in water or other corrosive fluids. Also, it should have good moisture stability. Pumps that meet such service requirements are usually integrally self-contained; that is, they are driven by enclosed motors sealed for environmental protection.
In addition to these demanding requirements, there is the general problem of making submersible pumps at reasonable cost. As usually found in manufacturing processes, secondary operations involved in the making of component parts, such as drilling and tapping holes, add large labor and overhead economic burdens. Especially bothersome in the making of pumps has been the alignment problems encountered during assembly operations. It is not unusual during the assembly of pump components for trained personnel to press, shave, strike, and otherwise adjust component parts so as to obtain proper adjustment for each individual pump. This is not only time consuming, it also introduces variations in pump operation due to the component tolerances summing to give a wider span of operating performance, thereby making prediction of pump performance more difficult.
Another problem encountered in submersible pumps is heat buildup due to the enclosed motor as well as from the friction of bearing surfaces. This heat may affect operating characteristics as well as shorten the effective operating life of the pump and motor assembly. Therefore, the heat created by the working parts of a submersible pump must be removed to give stable and safe operation.
Another problem that presents itself with submersible pumps is that of maintaining the exterior surfaces so that the pump retains its appearance. In a consumer market, color often becomes a decisive factor and, accordingly, submersible pumps must be designed with that in mind. Generally speaking, painted surfaces have not always succeeded in such service, and a good paint coating that will meet the rigorous test of endurance is an expensive ingredient in the manufacture of submersible pumps.
In addition to the above, there is a need for submersible pumps to be constructed in a manner that assures complete electrical integrity; that is, submersible pumps should be constructed with the advantages of the best features of grounding and, preferably, constructed in compliance with the double insulation principle. As to the latter, this refers to the technique of insulating each part of the assembly from the electrical motor such that the motor is completely isolated electrically and, further, each potential conductor is insulated. This requirement for submersible pumps has arisen from the experience of electrical shorting whenever portions of electrical insulation are broken down due to wear, fatigue or the like, whereupon electrical leakage has occurred. Of course, in the case of submersible pumps, the danger presented from such electrical leakage is increased by the possibility of conducting such leakage through the submerging fluid.